Recently, with the increase in performance of semiconductor elements due to their miniaturization or three-dimensionalization, there has been a trend that semiconductor elements consume a high electric power. Accordingly, semiconductor elements are likely to generate heat, and therefore the importance of a technique to efficiently release generated heat is growing.
Heretofore, as a resin film for semiconductor elements such as a surface protection film or an interlayer insulating film of semiconductor elements, a polyimide resin having an excellent heat resistance, mechanical property, etc. has been widely used (e.g. Patent Document 1). However, such a polyimide resin is likely to have an insufficient thermal conductivity, and therefore there is a problem such that the pace for improvement in performance of semiconductor elements has been declined.
Further, there is a report that it becomes possible to significantly increase thermal conductivity by controlling the high-order structure of an epoxy resin (e.g. Patent Document 2). However, there has been a problem such that the heat resistance of the epoxy resin is not sufficient for its use in a resin film for semiconductor elements.
Accordingly, for example, it has been attempted to increase the thermal conductivity of a resin film for semiconductor elements by using a polyimide resin having liquid crystallinity (e.g. Patent Documents 3 to 5).